Electrical submersible well pumps for deep wells are normally installed within casing on a string of tubing. Usually the tubing is made up of sections of pipe screwed together. Coil tubing deployed from a reel is also used to a lesser extent. The motor is supplied with power through a power cable that is strapped alongside the tubing. The pump is typically located above the motor, is connected to the lower end of the tubing, and pumps fluid through the tubing to the surface. One type of a pump is a centrifugal pump using a large number of stages, each stage having an impeller and a diffuser. Another type of pump, for lesser volumes, is a progressive cavity pump. This pump utilizes a helical rotor that is rotated inside an elastomeric stator which has double helical cavities. The stator is located inside a metal housing.
Periodically, the pump assembly must be pulled to the surface for repair or replacement. This involves pulling the tubing, which is time consuming. A workover rig is necessary for production tubing, and a coiled tubing unit is needed to pull coiled tubing. Often, the electrical motor needs no service, rather the service needs to be performed only on the pump. Sometimes the only change needed is to change the size of the pump without changing the size of the motor. However, the motor, being attached to the lower end of the pump, is also pulled along with the tubing. Damage to the power cable is not uncommon when pulling the tubing.